1. Field of the Invention
The present invention relates to a particulate matter detection device, and more particularly, it relates to a particulate matter detection device having a simple constitution and capable of accurately detecting a particulate matter.
2. Description of the Related Art
A flue exhaust gas and a diesel engine exhaust gas include a particulate matter (PM) such as soot, which has been a cause for air pollution. For the purpose of removing the particulate matter, a filter (a diesel particulate filter: DPF) made of a ceramic material and the like have widely been used. The DPF made of the ceramic material can be used for a long period of time, but defects such as cracks and melting damages due to thermal deterioration and the like might be generated, and the particulate matter might leak, although an amount thereof is a micro amount. When such defects are generated, from the viewpoint of the prevention of the air pollution, it is remarkably important to immediately detect the generation of the defects and to recognize the abnormality of a device.
As a method of detecting the generation of such defects, there has been suggested a method of disposing a particulate matter detection device on a downstream side of the DPF (see e.g. Patent Documents 1 and 2).
For example, the particulate matter detection device disclosed in Patent Document 1 includes a detection device main body which has a through hole formed in one end thereof and which is long in one direction, and at least a pair of electrodes embedded in a wall which forms this through hole and covered with a dielectric material. It is possible to electrically adsorb, by the wall surface of this through hole, a charged particulate matter included in a fluid flowing into the through hole, or a particulate matter charged by discharge which occurs in the through hole when a voltage is applied across the pair of electrodes, and included in the fluid flowing into the through hole. When a change of electric characteristics of the wall which forms the through hole is measured, it is possible to detect a mass of the particulate matter adsorbed by the wall surface of the through hole.
Consequently, the conventional particulate matter detection device allows the particulate matter included in a measurement target gas to adhere to and around the pair of electrodes which are sensors, and measures the change of the electric characteristics between the pair of electrodes, to detect the particulate matter in the measurement target gas.
[Patent Document 1] JP-A-2009-186278
[Patent Document 2] JP-A-2010-32488